Radio Interferometric Geolocation Miklos Maroti Peter Volgesi Sebestyen

Radio Interferometric Geolocation Miklos Maroti, Peter Volgesi, Sebestyen Dora Branislav Kusy, Gyorgy Balogh, Andras Nadas Karoly Molnar, Akos Ledeczi (Vanderbilt Univ. ) 2006. 11. 07. Tue. Presentor : Kim, Chanho Network Computing Laboratory

Contents One Line Summary Introduction RIPS (Radio Interferometric Positioning System) Source of Error Implementation Issues Range Calculation Localization Experiment Conclusion Network Computing Laboratory | 2 Korea Advanced Institute of Science and Technology

One Line Summary Introduce novel ranging technique (RIPS) for wireless sensor networks using application of the interference signal Network Computing Laboratory | 3 Korea Advanced Institute of Science and Technology

Introduction Many application of the WSN require individual nodes’ location State of Art Ultrasound method, Ultrasonic method, … Limitation : cannot have adequate accuracy , acceptable range at the same time / work in 2 D only Radio Interferometry High accuracy, long range Work in 3 D environment Network Computing Laboratory | 4 Korea Advanced Institute of Science and Technology

Introduction Terms Ranging: determine distances between nodes Localization: find physical 3 -D locations of nodes Interference: superposition of two or more waves resulting in a new wave pattern Interferometry: cross-correlates a signal from a single source recorded by 2 observers, used in geodesy, astronomy, … Network Computing Laboratory | 5 Korea Advanced Institute of Science and Technology

RIPS (Radio Interferometric Positioning System) RIPS no processing power to correlate high freq radio signals in WSN utilize two transmitters to produce low frequency interference signal directly Feasible on the highly resource constrained Achieve high accuracy Network Computing Laboratory | 6 Korea Advanced Institute of Science and Technology

RIPS (Radio Interferometric Positioning System) Phase Offset Caculate d. ABCD Central Localization Algorithm Localization Network Computing Laboratory | 7 Korea Advanced Institute of Science and Technology

Interferometric Positioning Network Computing Laboratory | 8 Korea Advanced Institute of Science and Technology

Sources of Error Carrier Frequency Inaccuracy Carrier Frequency Drift and Phase Noise Multipath effects Antenna Orientation RSSI measurement delay jitter RSSI Signal-to-Noise Ratio Signal Processing Error Time Synchronization Error Network Computing Laboratory | 9 Korea Advanced Institute of Science and Technology

RIPS implementation Steps 1. Selecting a pair of transmitters & scheduling 2. Calibration of the radios of senders 3. Transmission of a pure sine wave 4. Analysis of the RSSI samples of the interference signal at each of the receivers 5. Calculation of the actual d. ABCD range from the measured relative phase offset 6. Localization algorithm Network Computing Laboratory | 10 Korea Advanced Institute of Science and Technology

RIPS Implementation Issue (1/2) Radio Chipcon CC 1000 (433 MHz) Time Synchronization Crucial Operation : sampling of the RSSI signal (need to be aligned microseconds precision) Using external Synchronization protocol Network Computing Laboratory | 11 Korea Advanced Institute of Science and Technology

RIPS Implementation Issue (2/2) Tuning To measure interference accurately Implement a frequency tuning algorithm Frequency & Phase estimation RSSI values need to be processed on the motes Scheduling High Level Scheduling Responsible for selecting the pair of transmitters Should minimize the number of interference measurement Low Level Scheduling : Coordinates the activities of the two transmitters and multiple Frequency tuning algorithm, phase offset estimation requires proper timing Network Computing Laboratory | 12 Korea Advanced Institute of Science and Technology

Range Calculation Final d. ABCD = the solution with the minimum error value Network Computing Laboratory | 13 Korea Advanced Institute of Science and Technology

Localization Use an optimization method based on genetic algorithms (GA) Goal : find the relative positions of the nodes Requirement for this algorithm Given a set of nodes with unknown locations A set ‘M’ of d. ABCD ranges Output A node placement represented by a vector of (x, y, z) coordinates Using genetic operators to fix the error of solution Crossing over Mutations Network Computing Laboratory | 14 Korea Advanced Institute of Science and Technology

Experiments Setup 16 sensor nodes Area : 18 x 18 meter 3 anchor points Compare with high resolution DFT-based tone parameter estimation Network Computing Laboratory | 15 Korea Advanced Institute of Science and Technology

Experiments Error Distribution of all the ranges Calculating d. ABCD Network Computing Laboratory | 16 Korea Advanced Institute of Science and Technology

Experiments Error distribution of Localization Average : 3 cm Network Computing Laboratory | 17 Korea Advanced Institute of Science and Technology

Conclusion Introduce RIPS (Radio Interferometric Position System) which is the novel ranging technique for wireless sensor networks Achieve high accuracy, long range simultaneously Support 3 D localization, does not require extra HW or calibration Key Idea the application of interference signal Network Computing Laboratory | 18 Korea Advanced Institute of Science and Technology